LIGHT-EMITTING ELEMENT
A light-emitting element includes: a semiconductor layered structure including a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and an active layer located between the first semiconductor layer and the second semiconductor layer; a reflective portion including an insulative first layer located on the first semiconductor layer, a second layer made of a metal material located on the first layer, and a third layer located on the second layer; an insulative layer covering the reflective portion; a light-transmissive conductive layer located on the insulative layer and on the first semiconductor layer; a first electrode located on a portion of the light-transmissive conductive layer that is above the reflective portion; and a second electrode located on the second semiconductor layer.
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This application claims priority to Japanese Patent Application No. 2020-150139, filed on Sep. 7, 2020, the disclosure of which is hereby incorporated by reference in its entirety.
BACKGROUND 1. Technical FieldThe present disclosure relates to a light-emitting element.
2. Description of the Related ArtJapanese Patent Publication No. 2018-113442 describes a light-emitting element including a first electrode that is electrically connected to a first conductivity-type semiconductor layer, and a second electrode that is located on a transparent electrode layer provided on a second conductivity-type semiconductor layer and is electrically connected to the transparent electrode layer. The publication discloses a structure in which the second electrode includes a second electrode pad and a second electrode extended portion that is an extension from the second electrode pad, wherein a second reflective layer is provided between the second electrode and the transparent electrode layer to improve the light extraction efficiency.
SUMMARYWith such a light-emitting element, it is desirable to have a higher output power and a higher reliability. It is an object of the present disclosure to provide a light-emitting element having a higher output power and a higher reliability.
A light-emitting element according to one embodiment of the present disclosure includes: a semiconductor layered structure including a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and an active layer located between the first semiconductor layer and the second semiconductor layer; a reflective portion including an insulative first layer provided on the first semiconductor layer, a second layer made of a metal material provided on the first layer, and a third layer provided on the second layer; an insulative layer provided covering the reflective portion; a light-transmissive conductive layer provided on the insulative layer and on the first semiconductor layer; a first electrode provided on the light-transmissive conductive layer located above the reflective portion; and a second electrode provided on the second semiconductor layer.
According to certain embodiments of the present disclosure, it is possible to provide a light-emitting element having a higher output power and a higher reliability.
Embodiments of the light-emitting element according to the present disclosure will now be described. Note that the figures referred to in the following description are schematic representations in which the scale, interval, positional relationship, etc., of and between various members may be exaggerated. Some members may be omitted in some figures. Also, the scale and interval of and between various members may not be consistent between a plan view and a cross-sectional view thereof. Moreover, in the following description, like nomenclatures and like reference characters basically denote the same or similar members, for which detailed description will not be repeated.
As used herein, terms such as “on”, “above”, “upper” and “below” are intended merely to denote relative positions between components in the figures referred to in the description.
First EmbodimentA light-emitting element 1A according to the present embodiment includes: a semiconductor layered structure 12 including a first semiconductor layer 12a of the first conductivity type, a second semiconductor layer 12b of the second conductivity type, and an active layer 12c located between the first semiconductor layer 12a and the second semiconductor layer 12b; a reflective portion 13 including an insulative first layer 13a provided on the first semiconductor layer 12a, a second layer 13b made of a metal material provided on the first layer 13a, and a third layer 13c provided on the second layer 13b; an insulative layer 14 provided covering the reflective portion 13; a light-transmissive conductive layer provided on the insulative layer 14 and on the first semiconductor layer 12a; a first electrode 16 provided on the light-transmissive conductive layer 15 located above the reflective portion 13; and a second electrode 17 provided on the second semiconductor layer 12b.
Referring now to
(Substrate)
A substrate 11 is for supporting the semiconductor layered structure 12. The substrate 11 may be a growth substrate used for epitaxial growth of the semiconductor layered structure 12. The substrate 11 may be a sapphire (Al2O3) substrate in a case where a nitride semiconductor is used for the semiconductor layered structure 12, for example.
(Semiconductor Layered Structure)
As shown in
The semiconductor layered structure 12 includes an exposed portion 12d where the first semiconductor layer 12a and the active layer 12c are partially absent, i.e., a depression from the surface of the first semiconductor layer 12a such that the second semiconductor layer 12b is exposed upward through the first semiconductor layer 12a.
As shown in
The first semiconductor layer 12a, the second semiconductor layer 12b and the active layer 12c comprise a nitride semiconductor such as InxAlyGa1−x−yN (0≤X, 0≤Y and X+Y<1). For example, the semiconductor layered structure 12 may be made of a nitride semiconductor.
(Reflective Portion)
As shown in
The first layer 13a is in contact with the first semiconductor layer 12a. It is preferred that the first layer 13a is light-transmissive, has a lower refractive index than the first semiconductor layer 12a, and has a large refractive index difference from the first semiconductor layer 12a. Thus, at the interface between the first semiconductor layer 12a and the first layer 13a, light travelling from the active layer 12c toward the first layer 13a can be effectively reflected based on the refractive index difference and the Snell's law. This allows for reducing light absorption by the first electrode 16, thereby improving the light extraction efficiency. The first layer 13a may be a silicon oxide film (Si02) or a silicon oxynitride film (SiON), for example. For example, when a nitride semiconductor is used for the first semiconductor layer 12a, SiO2 is used as the first layer 13a.
The thickness of the first layer 13a may be set to be 80 nm or more and 300 nm or less, for example. By setting the thickness of the first layer 13a to 80 nm or more, it is possible to realize effective reflection at the interface between the first layer 13a and the first semiconductor layer 12a. By setting the thickness of the first layer 13a to 300 nm or less, it is possible to prevent the thickness of the reflective portion 13 including the first layer 13a from being too large, and to prevent breaking of the light-transmissive conductive layer 15 formed on the reflective portion 13. As used herein, the thickness of a member refers to the maximum thickness of the member in a cross-sectional view.
The second layer 13b is provided covering the upper surface of the first layer 13a. With the provision of the second layer 13b, light that passes through the first layer 13a without being reflected at the interface between the first layer 13a and the first semiconductor layer 12a can be reflected by means of the second layer 13b toward the first semiconductor layer 12a. This allows for improving the light extraction efficiency as compared with a case where the reflective portion 13 does not include the second layer 13b.
The second layer 13b is preferably made of a metal material having a high reflectivity for the peak wavelength of light from the active layer 12c. The second layer 13b comprises a metal material having a reflectivity of 70% or more, preferably 80% or more, for the peak wavelength of light from the active layer 12c, for example. The second layer 13b may comprise Al or Ag or an alloy including such a metal material, for example. The second layer may be made of Al, Ag or an alloy including Al or Ag as its primary component In view of suppressing dissolution of the second layer 13b to be described below, it is preferred to use AlCu, which has a better corrosion resistance than Al, as the second layer 13b. The thickness of the second layer 13b may be set to be 80 nm or more and 120 nm or less, for example.
The third layer 13c is provided covering the upper surface of the second layer 13b. With the provision of the third layer 13c, it is possible to suppress deterioration, e.g., oxidation, of the surface of the second layer 13b, and to prevent the reflectivity of the second layer 13b from lowering. The second layer 13b may possibly dissolve in a solution used in patterning, etc., in the step of forming the reflective portion 13 or in the step of forming the insulative layer 14. However, in the present embodiment, since the second layer 13b is covered by the third layer 13c, it is possible to suppress dissolution of the second layer 13b, and it is possible to further increase the reliability of the light-emitting element 1A.
The third layer 13c is preferably made of a light-transmissive insulative material. The third layer 13c may comprise SiO2 or SiON, for example. The thickness of the third layer 13c may be set to be 80 nm or more and 120 nm or less, for example. In view of improving the moisture resistance of the third layer 13c, it is preferred to use SiON as the third layer 13c.
The thickness of the reflective portion 13 is preferably set to 250 nm or more and 400 nm or less, for example. By setting the thickness of the reflective portion 13 to 250 nm or more, it is easier to realize the functions of different layers of the reflective portion 13 described above, and it is possible to increase the output power and the reliability of the light-emitting element 1A. By setting the thickness of the reflective portion 13 to be 400 nm or less, it is easier to prevent breaking of the light-transmissive conductive layer 15 formed to cover the area above the reflective portion 13, and it is possible to increase the reliability of the light-emitting element 1A.
(Insulative Layer)
As shown in
(Light-Transmissive Conductive Layer)
As shown in
The light-transmissive conductive layer 15 is preferably made of a conductive metal oxide. The light-transmissive conductive layer 15 may comprise an oxide that includes at least one element selected from the group consisting of Zn, In, Sn, Ga and Ti, for example. The light-transmissive conductive layer 15 may comprise ITO or ZnO, for example. ITO and ZnO have a high light-transmissive for visible light and have a high conductivity, and therefore are suitable materials for covering substantially the entire surface of the upper surface of the first semiconductor layer 12a.
In view of suppressing light absorption by the light-transmissive conductive layer 15, the light-transmissive conductive layer 15 preferably has a smaller thickness. The thickness of the light-transmissive conductive layer 15 may be 30 nm or more and 100 nm or less, preferably 35 nm or more and 80 nm or less, for example.
(First electrode)
As shown in
The first connecting portion 16a is an area used for external connection by wire bonding, or the like. The first connecting portion 16a has a generally circular shape in a top plan view as shown in
The first connecting portion 16a of the first electrode 16 may comprise Cu or Au or an alloy including such a metal as its primary component, for example, so as to be suitable for external connection by wire bonding, or the like. Note that the first connecting portion 16a and the first extended portion 16b of the first electrode 16 may be made of the same material.
(Second Electrode)
As shown in
As shown in
As shown in
(Protection Layer)
A protection layer 20 covers substantially the entire upper surface of the light-emitting element 1A. As shown in
A light-emitting element 1B according to the second embodiment will now be described with reference to
In the present embodiment, as shown in
The thickness of the second layer 13b and the thickness of the third layer 13c are each preferably smaller than the thickness of the first layer 13a. Therefore, the thickness of the reflective portion 13 can be made smaller as compared with a case where the first layer 13a, the second layer 13b and the third layer 13c have the same thickness. By decreasing the thickness of the reflective portion 13, it is easier to prevent breaking of the light-transmissive conductive layer 15, which is formed covering the area above the reflective portion 13, and it is possible to increase the reliability of the light-emitting element 13.
Third EmbodimentA light-emitting element 1C according to the third embodiment will now be described with reference to
As shown in
A light-emitting element 1D according to the fourth embodiment will now be described with reference to
As shown in
While embodiments of a light-emitting element of the present invention have been described above in detail, the scope of the present invention is not bound by the description herein, but rather should be construed broadly based on the appended claims. It should be understood that any of various changes and modifications based on the description herein shall fall within the scope of the present invention.
The light-emitting element of the present disclosure can suitably be used in various types of light sources, e.g., backlight light sources of liquid crystal display devices, various lighting apparatuses and large-sized display devices.
Claims
1. A light-emitting element comprising:
- a semiconductor layered structure comprising a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and an active layer located between the first semiconductor layer and the second semiconductor layer;
- a reflective portion comprising an insulative first layer located on the first semiconductor layer, a second layer made of a metal material located on the first layer, and a third layer located on the second layer;
- an insulative layer covering the reflective portion;
- a light-transmissive conductive layer located on the insulative layer and on the first semiconductor layer;
- a first electrode located on a portion of the light-transmissive conductive layer that is above the reflective portion; and
- a second electrode located on the second semiconductor layer.
2. The light-emitting element according to claim 1, wherein:
- the first electrode includes a first connecting portion and a first extended portion that extends from the first connecting portion; and
- the reflective portion is located between the first connecting portion and the first semiconductor layer, and between the first extended portion and the first semiconductor layer.
3. The light-emitting element according to claim 1, wherein a thickness of the first layer is larger than a thickness of the third layer.
4. The light-emitting element according to claim 2, wherein a thickness of the first layer is larger than a thickness of the third layer.
5. The light-emitting element according to claim 1, wherein an end portion of the second layer is covered by the third layer.
6. The light-emitting element according to claim 2, wherein an end portion of the second layer is covered by the third layer.
7. The light-emitting element according to claim 4, wherein an end portion of the second layer is covered by the third layer.
8. The light-emitting element according to claim 1, wherein a thickness of the insulative layer is larger than a thickness of the first layer.
9. The light-emitting element according to claim 2, wherein a thickness of the insulative layer is larger than a thickness of the first layer.
10. The light-emitting element according to claim 4, wherein a thickness of the insulative layer is larger than a thickness of the first layer.
11. The light-emitting element according to claim 1, wherein a width of the second layer is smaller than a width of the third layer in a cross-sectional view.
12. The light-emitting element according to claim 2, wherein a width of the second layer is smaller than a width of the third layer in a cross-sectional view.
13. The light-emitting element according to claim 1, wherein:
- the first layer is made of a silicon oxide film; and
- the insulative layer is made of a silicon oxynitride film.
14. The light-emitting element according to claim 2, wherein:
- the first layer is made of a silicon oxide film; and
- the insulative layer is made of a silicon oxynitride film.
15. The light-emitting element according to claim 3, wherein:
- the first layer is made of a silicon oxide film; and
- the insulative layer is made of a silicon oxynitride film.
16. The light-emitting element according to claim 1, wherein the second layer is made of Al, Ag or an alloy including Al or Ag as its primary component.
17. The light-emitting element according to claim 2, wherein the second layer is made of Al, Ag or an alloy including Al or Ag as its primary component.
18. The light-emitting element according to claim 1, wherein a thickness of the reflective portion is 250 nm or more and 400 nm or less.
Type: Application
Filed: Sep 3, 2021
Publication Date: Mar 10, 2022
Applicant: NICHIA CORPORATION (Anan-shi)
Inventors: Shun KITAHAMA (Tokushima-shi), Yusuke MINATO (Itano-gun)
Application Number: 17/466,680